1. Field of the Invention
The present invention relates to a stop lamp switch and particularly to a stop lamp switch that opens and closes contacts with movement of an actuating shaft.
2. Description of the Related Art
Brake lamps are generally provided in vehicles to signal vehicles behind the vehicle that braking is done. These brake lamps are lighted and extinguished by opening and closing contacts provided in a stop lamp switch operated by a brake pedal.
In a conventional stop lamp switch, the actuating shaft is linked to and moves in concert with a brake pedal, a case that movably holds the actuating shaft, a fixed contact provided in the case, and a movable contact provided on the actuating shaft that makes connection with the fixed contact with movement of the actuating shaft when the brake pedal is depressed. If dust or oil becomes attached between the fixed contact and the movable contact, it is not possible to establish proper electrical conduction between the contacts.
To prevent dust or oil from becoming between the fixed contact and the movable contact Japanese Patent Application Publication No. JP-A-2004-0714512 describes disposing a sealing member between the case and the actuated contacts. The sealing member is formed of an elastic material, such as rubber or elastomer, and is configured to enable displacement accompanying the movement of a sliding member. Because the fixed contact and the movable contact are isolated from the outside by the sealing member, the configuration is one intended to prevent the attachment of dust and oil between the contacts.
However, because the sealing member covering the fixed contact and movable contact is made of an elastic material such as rubber and because it deforms with movement of the actuating shaft, if the sealing member deteriorates with the passage of time, the quality of its sealing against dust decreases, so that there is a risk of not providing reliable prevention of dust and the like becoming attached to the contacts. Also, it is possible that the deterioration of the sealing member with the passage of time can bring with it generation of dust from the sealing member, and attachment of the dust to the contacts can impede the proper operation of the contacts.